Method of vaporizing a getter in an evacuated vessel



Patented May 3, 1927.

UNITED STATES PATENT OFFICE.

WILLIAM HENRY TOWNE HOLDEN, OF NEW YORK, N. Y., ASSIGNOR TO WESTINGHOUSE LAM]? COMPANY, A CORPORATION OF PENNSYLVANIA.

METHOD OF VAPORIZIN G A GETTER IN AN EVACUATED VESSEL.

No Drawing This invention relates to electrical devices and particularly to discharge tubes of the gas-tilled type. 1

One object of my invention is to provide a method for expeditiously purifying the gas in an electrical-discharge device employing a single electrode.

Another object of the invention is to provide a temporary external electrode in cooperation with a single-electrode tube for the purpose of passing a current through said tube.

This invention is particularly advantageous in connection with a discharge tube having a gaseous atmosphere which will readily glow upon the passage of a slight current therethrough. In tubes of this type, sensitiveness is required in order that difl'erences in potential of only a few hundred volts may be detected and a comparatively high degree of purity of gaseous atmosphere is therefore necessary.

It has not been found convenient or practical to purify the gas previous to its introduction into the tube; inasmuch as pure neon gas is difficult and expensive to obtain, furthermore, great care and time are necessary to introduce such pure gas into a tube without contamination and costly and special apparatus are required. It is therefore desirable to remove deleterious substances from the gas after the tube has been sealed.

In tubes having two electrodes, this is generally accomplished by placing a selected chemical substance or getter material such as magnesium, calcium or the like,

upon one or both of the electrodes within the tube prior to the sealing thereof.

The getter material is then vaporized by the passage of a current through the tube. lYhile in this state of vaporization, the getter combines chemically with the active gases within the tube or the liberated gases to form nonvolatile compounds or reaction products having low vapor pressure.

in the above mentioned tube which employs two electrodes, this vaporization of the getter material is accomplished by placing the electrodes in circuit with a hightension source, the action of the electric discharge passing between the electrodes'resulting in the etter material being vaporized, as it has ieen found that the current has a tendency to pass through the getter Application filed March 23, 1922. Serial No. 546,203.

material in preference to the electrodes. By reason of this phenomenon,the getter material is heated to its vaporization temperature and a cleaning-up action takes place.

My invention, however, relates particularly to the vaporization of a getter material within a tube employing'a single electrode. In a tube of this character, it is necessary to pass sufficient current therethrough to raise the electrode to a temperature high enough to vaporize the chemical I cient current passed through thetube to heat the electrode or getter material and vaporize the chemical substance.

In practice, an electrode is sealed into a tube in the usual manner and a vaporizable chemical substance is then deposited within the tube, preferably upon the electrode. The tube is then filled with a selected gas and sealed. These steps are common to the manufacture of a discharge tube and my invention relates to the next operation or step which consists in activating the getter ma terial. The tube is then placed in close proxin'iity to theexternal electrode and a l1igl1frequency potential is applied to the electrodes. It is preferable toemploy a high-frequency as, for example, of the order of one million cycles.

A tube, having thus been treated, may be removed from the temporary electrode and another tube disposed adjacent thcretofor treatn'ient. It will be readily appreciated that, by my simple and effective method of activating a getter material within a single electrode tube, I overcome various disadvantages which result from the necessity of purifying the gas previous to its introduction into the tube, as would otherwise be necessary.

Although the present invention is particularly described as a method of activating getter material in a discharge tube, it

is to be understood that the method may have general application when it is desirable to activate a chemical substance in a hollow body by the passage of a current therethrough and where it is not possible by ordinary method to pass suflicient current through the body to heat the electrode or chemical substance to the necessary temperature. I

\Vhatis claimed is: 1. The method of purifying the atmosphere in a discharge tube employing a single electrode which consists in, depositing, a vaporizable chemlcal substance upon said electrode, sealing-off said tube, disposing a supplemental electrode adjacent thereto and passing a high-frequenc current through said electrodes to vaporize said substance.

2. The method of purifying the gaseous atmosphere in a discharge tube having a. single electrode which consists in depositin a vaporiaablechemical substance within'sai tube, sealingoff said tube, disposing a temnesium which is chemically active with respect to deleterious substances Within said tube to form non-volatile compounds, exhausting and filling said tube with a gas, sealing-off said tube and disposing adjacent thereto a temporary external electrode and passing a high-frequency current through said electrodes to vaporize said magnesium.

'- In testimony whereof, I have hereunto subscribed my name'this 22nd day of March,

WILLIAM HENRY 'TOWNE HOLDEN. 

